This invention relates to an icecream-making appliance for domestic use which comprises an icecreaming vessel, an icecreaming paddle driven by an electric motor and operative within said icecreaming vessel, and a device effective to discontinue the mechanical action of said paddle automatically.
In icecream making machines, the mechanical action of the paddle must be stopped as soon as the icecream is completed; as is known, icecream is to be regarded as completed on its achieving a certain consistency (or viscosity), which may differ according to the type of the icecream and individual consumer's taste.
If the machine is stopped prematurely, the icecream will show poor consistency (incomplete icecreaming) and hence, be of inferior quality. If, by contrast, the machine is stopped too late, the quality of the icecream remains unaffected, but the mechanical components, and the paddle motor especially, are subjected to unnecessary and objectionable stresses, while valuable electric power is wasted. As is apparent, the latter situation would be met virtually each time that icecream is prepared upon re-starting the machine on account of incomplete icecreaming.
In an attempt to solve this problem, some devices have been proposed and used.
One of these prior devices provides for the use, for example, of an icecreaming paddle having tiltable working portions, the tilting movement of said working portions being controlled by spring mechanisms.
On the paddle meeting a preset mechanical resistance, the working portions thereof are tilted into an inoperative position, usually outward of the icecream mass. Such devices reduce the unnecessary stresses and waste of power (the motor continuing to turn, but under a reduced load, and hence, at a reduced rate of electric power consumption). However, they are not devoid of some well-recognised disadvantages, the most important of which is the need for calibrating the spring mechanisms which control the tilting movement. As is well known in the art, that calibration is a fairly critical and difficult operation, and is generally factory set without allowance for manipulation by the user; it may be appreciated that this approach restricts the choice of the icecream consistency which is more appropriate in each case. In addition, incidental external factors (such as the ageing of parts) may change in an uncontrollable manner the time when the consistency of the icecream mass causes the working portions of the icecreaming paddle to tilt out.
Other devices included are timers by means of which a given period of operation can be preset. At the end of that period, the paddle is stopped by disengagement from the motor, which continues instead to be operated.
The above period of operation should be selected based upon previous experience (either made directly by the user or by the manufacturer and tabulated in special recipe books), and is of necessity a rough approximation since it cannot take into account such random events as temperature, humidity, granulometry, and hardness of the water. Further, in the instance of some novel recipe being attempted, the tested values require to be extrapolated, which introduces well recognized factors of uncertainty connected with this type of operation. Thus, it often happens that the set period of time be either too short or too long, thereby the cited problems (mechanical stresses, power consumption) are at most attenuated, but surely not eliminated.
Accordingly, still unsolved is the problem of providing an icecream-making apparatus which incorporates a stop device effective to cut in at the exact time when the icecream is ready, i.e. on its reaching the consistency sought by the user.